diff --git a/src/middleware.test.ts b/src/middleware.test.ts
index 1195f07..c73fb62 100644
--- a/src/middleware.test.ts
+++ b/src/middleware.test.ts
@@ -132,6 +132,36 @@ describe("auth routes", () => {
     expect(target?.searchParams.get("redirect")).toBeNull();
   });
 
+  it("rejects malicious, protocol-relative, or external redirect URLs and falls back to /dashboard", () => {
+    const maliciousCases = [
+      "//evil.com",
+      "//evil.com/path",
+      "https://evil.com",
+      "http://evil.com",
+      "javascript:alert(1)",
+      "data:text/html,evil",
+      "\\evil.com",
+      "relative-without-slash",
+    ];
+
+    for (const evil of maliciousCases) {
+      const target = redirectTarget(
+        middleware(makeRequest("/connect", "jwt-abc", `?redirect=${encodeURIComponent(evil)}`))
+      );
+      expect(target?.pathname).toBe("/dashboard");
+    }
+  });
+
+  it("allows safe internal redirect paths", () => {
+    const safeCases = ["/rewards", "/courses/123", "/credentials/my-cred"];
+    for (const safe of safeCases) {
+      const target = redirectTarget(
+        middleware(makeRequest("/connect", "jwt-abc", `?redirect=${encodeURIComponent(safe)}`))
+      );
+      expect(target?.pathname).toBe(safe);
+    }
+  });
+
   it("leaves /onboarding accessible while signed out", () => {
     expect(redirectTarget(middleware(makeRequest("/onboarding")))).toBeNull();
   });
diff --git a/src/middleware.ts b/src/middleware.ts
index 084db2b..61d6895 100644
--- a/src/middleware.ts
+++ b/src/middleware.ts
@@ -31,6 +31,22 @@ function isAuthRoute(pathname: string): boolean {
   return AUTH_PREFIXES.some((prefix) => pathname.startsWith(prefix));
 }
 
+/**
+ * Validate and sanitize redirect destination to prevent open redirects (issue #518).
+ * Must start with a single '/' and not be protocol-relative ('//') or specify a URL scheme.
+ */
+export function getSafeRedirect(redirect: string | null): string {
+  if (!redirect) return "/dashboard";
+  if (!redirect.startsWith("/") || redirect.startsWith("//") || redirect.includes("\\")) {
+    return "/dashboard";
+  }
+  // Reject protocol schemes e.g. "http:", "https:", "javascript:", "data:"
+  if (/^[a-zA-Z][a-zA-Z0-9+.-]*:/.test(redirect)) {
+    return "/dashboard";
+  }
+  return redirect;
+}
+
 export function middleware(request: NextRequest) {
   const { pathname } = request.nextUrl;
   const sessionToken = request.cookies.get("chainlearn-session")?.value;
@@ -52,7 +68,7 @@ export function middleware(request: NextRequest) {
     if (sessionToken) {
       const redirect = request.nextUrl.searchParams.get("redirect");
       const url = request.nextUrl.clone();
-      url.pathname = redirect || "/dashboard";
+      url.pathname = getSafeRedirect(redirect);
       url.searchParams.delete("redirect");
       return NextResponse.redirect(url);
     }